| 1 | 1 | class Zipper: |
| 2 | | # Tree is a dict with keys "value" (int), "left" (dict or None), "right" (dict or None) |
| 2 | """ |
| 3 | A zipper for navigating and manipulating a binary tree. |
| 4 | |
| 5 | The zipper maintains a focus on a specific node in the tree, allowing |
| 6 | navigation and modifications while preserving the tree's structure. |
| 7 | """ |
| 8 | |
| 9 | def __init__(self, tree, path=None): |
| 10 | """ |
| 11 | Initialize a Zipper. |
| 12 | |
| 13 | Args: |
| 14 | tree (dict): The binary tree represented as a dict with keys 'value', 'left', 'right'. |
| 15 | path (list): A list of tuples representing the path from root to focus node. |
| 16 | Each tuple contains (parent_node, direction) where direction is 'left' or 'right'. |
| 17 | """ |
| 18 | self.tree = tree |
| 19 | self.path = path or [] |
| 20 | |
| 3 | 21 | @staticmethod |
| 4 | 22 | def from_tree(tree: dict) -> "Zipper": |
| 5 | | pass |
| 6 | | |
| 23 | """ |
| 24 | Create a zipper from a binary tree. |
| 25 | |
| 26 | Args: |
| 27 | tree (dict): The binary tree to create a zipper for. |
| 28 | |
| 29 | Returns: |
| 30 | Zipper: A new zipper with focus on the root node. |
| 31 | |
| 32 | Edge Case: Empty tree (None) is handled by creating an empty path. |
| 33 | """ |
| 34 | # Edge Case: Handle None tree |
| 35 | if tree is None: |
| 36 | return Zipper({}, []) |
| 37 | return Zipper(tree, []) |
| 38 | |
| 39 | def _get_focus_node(self): |
| 40 | """ |
| 41 | Get the current focus node by following the path from root. |
| 42 | |
| 43 | Returns: |
| 44 | dict: The focus node, or None if the path leads to a None node. |
| 45 | """ |
| 46 | node = self.tree |
| 47 | for parent, direction in self.path: |
| 48 | if node is None: |
| 49 | return None |
| 50 | node = node.get(direction) |
| 51 | return node |
| 52 | |
| 7 | 53 | def value(self) -> int: |
| 8 | | pass |
| 9 | | |
| 54 | """ |
| 55 | Get the value of the focus node. |
| 56 | |
| 57 | Returns: |
| 58 | int: The value of the focus node. |
| 59 | |
| 60 | Edge Case: If focus node is None, this would raise an error in a real implementation, |
| 61 | but according to problem constraints, we assume valid operations. |
| 62 | """ |
| 63 | node = self._get_focus_node() |
| 64 | return node["value"] |
| 65 | |
| 10 | 66 | def set_value(self, value: int) -> "Zipper": |
| 11 | | pass |
| 12 | | |
| 67 | """ |
| 68 | Set the value of the focus node. |
| 69 | |
| 70 | Args: |
| 71 | value (int): The new value for the focus node. |
| 72 | |
| 73 | Returns: |
| 74 | Zipper: A new zipper with the updated value. |
| 75 | |
| 76 | Edge Case: If focus node is None, this would not work correctly, but we assume valid operations. |
| 77 | """ |
| 78 | # Create a deep copy of the tree |
| 79 | new_tree = self._deep_copy_tree(self.tree) |
| 80 | |
| 81 | # Navigate to the focus node in the copied tree |
| 82 | node = new_tree |
| 83 | for parent, direction in self.path: |
| 84 | node = node[direction] |
| 85 | |
| 86 | # Update the value |
| 87 | node["value"] = value |
| 88 | |
| 89 | return Zipper(new_tree, list(self.path)) |
| 90 | |
| 13 | 91 | def left(self) -> "Zipper | None": |
| 14 | | pass |
| 15 | | |
| 92 | """ |
| 93 | Move the focus to the left child of the current focus node. |
| 94 | |
| 95 | Returns: |
| 96 | Zipper | None: A new zipper with focus on the left child, or None if no left child exists. |
| 97 | |
| 98 | Edge Case: If focus node is None or has no left child, return None. |
| 99 | """ |
| 100 | node = self._get_focus_node() |
| 101 | # Edge Case: Focus node is None or has no left child |
| 102 | if node is None or node.get("left") is None: |
| 103 | return None |
| 104 | |
| 105 | new_path = list(self.path) |
| 106 | new_path.append((node, "left")) |
| 107 | return Zipper(self.tree, new_path) |
| 108 | |
| 16 | 109 | def set_left(self, tree: dict | None) -> "Zipper": |
| 17 | | pass |
| 18 | | |
| 110 | """ |
| 111 | Set the left child of the focus node. |
| 112 | |
| 113 | Args: |
| 114 | tree (dict | None): The new left subtree. |
| 115 | |
| 116 | Returns: |
| 117 | Zipper: A new zipper with the updated left child. |
| 118 | |
| 119 | Edge Case: If focus node is None, this would not work correctly, but we assume valid operations. |
| 120 | """ |
| 121 | # Create a deep copy of the tree |
| 122 | new_tree = self._deep_copy_tree(self.tree) |
| 123 | |
| 124 | # Navigate to the focus node in the copied tree |
| 125 | node = new_tree |
| 126 | for parent, direction in self.path: |
| 127 | node = node[direction] |
| 128 | |
| 129 | # Update the left child |
| 130 | node["left"] = tree |
| 131 | |
| 132 | return Zipper(new_tree, list(self.path)) |
| 133 | |
| 19 | 134 | def right(self) -> "Zipper | None": |
| 20 | | pass |
| 21 | | |
| 135 | """ |
| 136 | Move the focus to the right child of the current focus node. |
| 137 | |
| 138 | Returns: |
| 139 | Zipper | None: A new zipper with focus on the right child, or None if no right child exists. |
| 140 | |
| 141 | Edge Case: If focus node is None or has no right child, return None. |
| 142 | """ |
| 143 | node = self._get_focus_node() |
| 144 | # Edge Case: Focus node is None or has no right child |
| 145 | if node is None or node.get("right") is None: |
| 146 | return None |
| 147 | |
| 148 | new_path = list(self.path) |
| 149 | new_path.append((node, "right")) |
| 150 | return Zipper(self.tree, new_path) |
| 151 | |
| 22 | 152 | def set_right(self, tree: dict | None) -> "Zipper": |
| 23 | | pass |
| 24 | | |
| 153 | """ |
| 154 | Set the right child of the focus node. |
| 155 | |
| 156 | Args: |
| 157 | tree (dict | None): The new right subtree. |
| 158 | |
| 159 | Returns: |
| 160 | Zipper: A new zipper with the updated right child. |
| 161 | |
| 162 | Edge Case: If focus node is None, this would not work correctly, but we assume valid operations. |
| 163 | """ |
| 164 | # Create a deep copy of the tree |
| 165 | new_tree = self._deep_copy_tree(self.tree) |
| 166 | |
| 167 | # Navigate to the focus node in the copied tree |
| 168 | node = new_tree |
| 169 | for parent, direction in self.path: |
| 170 | node = node[direction] |
| 171 | |
| 172 | # Update the right child |
| 173 | node["right"] = tree |
| 174 | |
| 175 | return Zipper(new_tree, list(self.path)) |
| 176 | |
| 25 | 177 | def up(self) -> "Zipper | None": |
| 26 | | pass |
| 27 | | |
| 178 | """ |
| 179 | Move the focus to the parent of the current focus node. |
| 180 | |
| 181 | Returns: |
| 182 | Zipper | None: A new zipper with focus on the parent, or None if focus is already at root. |
| 183 | |
| 184 | Edge Case: If focus is at root (no parent), return None. |
| 185 | """ |
| 186 | # Edge Case: Already at root (no parent) |
| 187 | if not self.path: |
| 188 | return None |
| 189 | |
| 190 | new_path = list(self.path) |
| 191 | new_path.pop() |
| 192 | return Zipper(self.tree, new_path) |
| 193 | |
| 28 | 194 | def to_tree(self) -> dict: |
| 29 | | pass |
| 195 | """ |
| 196 | Get the complete tree from the zipper. |
| 197 | |
| 198 | Returns: |
| 199 | dict: The complete binary tree. |
| 200 | """ |
| 201 | return self.tree |
| 202 | |
| 203 | def _deep_copy_tree(self, tree): |
| 204 | """ |
| 205 | Create a deep copy of a binary tree. |
| 206 | |
| 207 | Args: |
| 208 | tree (dict): The tree to copy. |
| 209 | |
| 210 | Returns: |
| 211 | dict: A deep copy of the tree. |
| 212 | """ |
| 213 | if tree is None: |
| 214 | return None |
| 215 | |
| 216 | copied = { |
| 217 | "value": tree["value"], |
| 218 | "left": self._deep_copy_tree(tree.get("left")), |
| 219 | "right": self._deep_copy_tree(tree.get("right")) |
| 220 | } |
| 221 | return copied |
| 222 | |
| 223 | # Handled Edge Cases: Empty tree, None focus node, No left child, No right child, Already at root |